Atlantoaxial Fusion Using C1 Sublaminar Cables and C2 Translaminar Screws

Atlantoaxial Fusion Using C1 Sublaminar Cables and C2 Translaminar Screws Abstract BACKGROUND Atlantoaxial instability, which can arise in the setting of trauma, degenerative diseases, and neoplasm, is often managed surgically with C1–C2 arthrodesis. Classical C1–C2 fusion techniques require placement of instrumentation in close proximity to the vertebral artery and C2 nerve root. OBJECTIVE To report a novel C1–C2 fusion technique that utilizes C2 translaminar screws and C1 sublaminar cables to decrease the risk of injury to the vertebral artery and C2 nerve root. METHODS To facilitate fixation to the atlas, while minimizing the risk of injury to the vertebral artery and to the C2 nerve root, we sought to determine the feasibility of using a soft cable around the C1 arch and affixing it to a rod connected to C2 laminar screws. We reviewed our experience in 3 patients. RESULTS We used this technique in patients in whom we anticipated difficult C1 screw placement. Three patients were identified through a review of the senior author's cases. Atlantoaxial instability was associated with trauma in 2 patients and chronic degenerative changes in 1 patient. Common symptoms on presentation included pain and limited range of motion. All patients underwent C1–C2 fusion with C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1. There were no reports of postoperative complications or hardware failure. CONCLUSION We demonstrate a novel, technically straightforward approach for C1–C2 fusion that minimizes risk to the vertebral artery and to the C2 nerve root, while still allowing for semirigid fixation in instances of both traumatic and chronic degenerative atlantoaxial instability. Arthrodesis, Atlantoaxial instability, Fusion, Translaminar ABBREAVIATIONS ABBREAVIATIONS ADI atlantodental interval CT computed tomography Atlantoaxial instability is a condition that arises in a variety of pathologies including trauma, neoplasm, congenital malformations, and degenerative and inflammatory diseases.1-4 Surgical techniques for atlantoaxial fusion have evolved over many decades (see Table 1) since the first technique utilizing stout braided silk to fasten the posterior arch of C1 to the spinous process of C2 was described by Mixter and Osgood in 1910.5 In 1937, Gallie6,7 expanded upon this method by using a threaded steel wire in a similar conformation, and also using the wire to stabilize autologous iliac bone graft placed within the posterior elements of C1 and C2.8,9 Other popular wiring techniques include the Brooks and Jenkins (bilateral iliac crest bone grafts with bilateral sublaminar wires)10 and the Sonntag (sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft).11 Screw fixation methods, which are associated with higher rates of fusion, were later developed.12-18 The techniques include C1–C2 transarticular screw placement (Magerl)19 and C1 lateral mass screw placement in combination with C2 pars or pedicle screws (Goel20,21). However, these techniques increase the risk of vertebral artery injury and can involve either compression or sacrifice of the C2 nerve roots.22-25 An alternative method of fixation to C2 involving translaminar screw placement was described by Wright et al in 2004.1 This method avoids the risk of a vertebral artery injury and has been used as a basis for C1–C2 constructs involving C1 lateral mass screws and C2-subaxial cervical spine fusion constructions. We have since adapted the translaminar C2 screw technique in combination with C1 translaminar cable suspension for C1–C2 fusion in the setting of atlantoaxial instability. This technique offers technical simplicity and decreases the risk of vertebral artery injury while also obviating C2 nerve root sacrifice or compression. Here, we describe our technique and initial success in the treatment of patients with atlantoaxial instability. TABLE 1. Historical Summary of Techniques for C1–C2 Fixation Technique  Surgeon, Ref. (year)  Advantage  Shortcoming  Wire or cable placement    Stout braided silk to fasten the posterior arch of C1 to spinous process of C2  Mixter and Osgood5 (1910)  Innovative use of wire for stabilization.  Poor stability in all planes, low likelihood of arthrodesis without bone grafting. Prolonged immobilization.  Iliac bone graft placed above C2 spinous process and abutting posterior C1 arch secured by a steel wire looping around C1 posterior arch and C2 spinous process  Gallie6 (1937)  Technical simplicity. Stability with flexion and extension.  Poor rotational stability compared to Brooks and Jenkins and Magerl technique.33 Increased rate of nonunion compared to screw fixation.40,41 Requires postoperative rigid immobilization.33 Difficult to use in posteriorly displaced C1.11  Bilateral iliac crest bone grafts secured with bilateral sublaminar wires looping under posterior arches of C1 and C2  Brooks and Jenkins10 (1978)  Improved fixation compared to the Gallie technique.42 Technical simplicity.  Increased risk of neural injury with passage of 2 bone grafts. Increased rate of nonunion compared to screw fixation.41 Requires postoperative rigid immobilization.33  Sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft  Sonntag11 (1991)  Avoidance of bilateral bone grafts and use of single loop of wire with decreased risk of injury to neural or vascular structures compared to the Gallie and Brooks and Jenkins technique.11  Requires postoperative rigid immobilization.11  Screw Placement  C1–C2 transarticular screw placement  Magerl19 (1987)  First proposed screw fixation method with improved stability and fusion rates over wire fixation alone.16,33 Technically challenging.  Increased risk of vertebral artery injury.3,4,24,27,32 Risk of compression or sacrifice of the C2 nerve roots.43 Risk of damage to the dura.22,44  C1 lateral mass screw placement in combination with C2 pars or pedicle screws with C2  Goel20,21 (1994)  Anatomic alignment of C1–C2 complex not necessary prior to procedure. High fusion rate reported (100%).21 Decreased risk of injury to vertebral artery compared to the Magerl technique.20  Risk of vertebral artery injury.4,27,32 Risk of compression or sacrifice of the C2 nerve roots.43  Bilateral, crossing C2 translaminar screw placement  Wright1 (2004)  Can be used in the setting of aberrant vertebral artery. Decreased risk to vertebral artery compared to earlier screw methods.3 In large case series, high fusion rate (97.6%)3 and lower breach of C2 lamina (1.3%) compared to pedicle screws (7%).45  Increased incidence of reoperation (6.1%) when used in subaxial constructs when compared to pedicle screws (0%).45 Risk of violation of inner laminar cortex with screw placement.34  C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1  Current series (2016)  Decreased risk to vertebral artery and C2 nerve roots compared to earlier screw fixation methods. Can be used in the setting of aberrant vertebral artery. Technical feasibility. Allows for direct visual monitoring of laminar cortical bone to avoid breach.  Not amenable in cases of C1 arch fracture or bifid C1 arch.  Technique  Surgeon, Ref. (year)  Advantage  Shortcoming  Wire or cable placement    Stout braided silk to fasten the posterior arch of C1 to spinous process of C2  Mixter and Osgood5 (1910)  Innovative use of wire for stabilization.  Poor stability in all planes, low likelihood of arthrodesis without bone grafting. Prolonged immobilization.  Iliac bone graft placed above C2 spinous process and abutting posterior C1 arch secured by a steel wire looping around C1 posterior arch and C2 spinous process  Gallie6 (1937)  Technical simplicity. Stability with flexion and extension.  Poor rotational stability compared to Brooks and Jenkins and Magerl technique.33 Increased rate of nonunion compared to screw fixation.40,41 Requires postoperative rigid immobilization.33 Difficult to use in posteriorly displaced C1.11  Bilateral iliac crest bone grafts secured with bilateral sublaminar wires looping under posterior arches of C1 and C2  Brooks and Jenkins10 (1978)  Improved fixation compared to the Gallie technique.42 Technical simplicity.  Increased risk of neural injury with passage of 2 bone grafts. Increased rate of nonunion compared to screw fixation.41 Requires postoperative rigid immobilization.33  Sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft  Sonntag11 (1991)  Avoidance of bilateral bone grafts and use of single loop of wire with decreased risk of injury to neural or vascular structures compared to the Gallie and Brooks and Jenkins technique.11  Requires postoperative rigid immobilization.11  Screw Placement  C1–C2 transarticular screw placement  Magerl19 (1987)  First proposed screw fixation method with improved stability and fusion rates over wire fixation alone.16,33 Technically challenging.  Increased risk of vertebral artery injury.3,4,24,27,32 Risk of compression or sacrifice of the C2 nerve roots.43 Risk of damage to the dura.22,44  C1 lateral mass screw placement in combination with C2 pars or pedicle screws with C2  Goel20,21 (1994)  Anatomic alignment of C1–C2 complex not necessary prior to procedure. High fusion rate reported (100%).21 Decreased risk of injury to vertebral artery compared to the Magerl technique.20  Risk of vertebral artery injury.4,27,32 Risk of compression or sacrifice of the C2 nerve roots.43  Bilateral, crossing C2 translaminar screw placement  Wright1 (2004)  Can be used in the setting of aberrant vertebral artery. Decreased risk to vertebral artery compared to earlier screw methods.3 In large case series, high fusion rate (97.6%)3 and lower breach of C2 lamina (1.3%) compared to pedicle screws (7%).45  Increased incidence of reoperation (6.1%) when used in subaxial constructs when compared to pedicle screws (0%).45 Risk of violation of inner laminar cortex with screw placement.34  C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1  Current series (2016)  Decreased risk to vertebral artery and C2 nerve roots compared to earlier screw fixation methods. Can be used in the setting of aberrant vertebral artery. Technical feasibility. Allows for direct visual monitoring of laminar cortical bone to avoid breach.  Not amenable in cases of C1 arch fracture or bifid C1 arch.  View Large TABLE 1. Historical Summary of Techniques for C1–C2 Fixation Technique  Surgeon, Ref. (year)  Advantage  Shortcoming  Wire or cable placement    Stout braided silk to fasten the posterior arch of C1 to spinous process of C2  Mixter and Osgood5 (1910)  Innovative use of wire for stabilization.  Poor stability in all planes, low likelihood of arthrodesis without bone grafting. Prolonged immobilization.  Iliac bone graft placed above C2 spinous process and abutting posterior C1 arch secured by a steel wire looping around C1 posterior arch and C2 spinous process  Gallie6 (1937)  Technical simplicity. Stability with flexion and extension.  Poor rotational stability compared to Brooks and Jenkins and Magerl technique.33 Increased rate of nonunion compared to screw fixation.40,41 Requires postoperative rigid immobilization.33 Difficult to use in posteriorly displaced C1.11  Bilateral iliac crest bone grafts secured with bilateral sublaminar wires looping under posterior arches of C1 and C2  Brooks and Jenkins10 (1978)  Improved fixation compared to the Gallie technique.42 Technical simplicity.  Increased risk of neural injury with passage of 2 bone grafts. Increased rate of nonunion compared to screw fixation.41 Requires postoperative rigid immobilization.33  Sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft  Sonntag11 (1991)  Avoidance of bilateral bone grafts and use of single loop of wire with decreased risk of injury to neural or vascular structures compared to the Gallie and Brooks and Jenkins technique.11  Requires postoperative rigid immobilization.11  Screw Placement  C1–C2 transarticular screw placement  Magerl19 (1987)  First proposed screw fixation method with improved stability and fusion rates over wire fixation alone.16,33 Technically challenging.  Increased risk of vertebral artery injury.3,4,24,27,32 Risk of compression or sacrifice of the C2 nerve roots.43 Risk of damage to the dura.22,44  C1 lateral mass screw placement in combination with C2 pars or pedicle screws with C2  Goel20,21 (1994)  Anatomic alignment of C1–C2 complex not necessary prior to procedure. High fusion rate reported (100%).21 Decreased risk of injury to vertebral artery compared to the Magerl technique.20  Risk of vertebral artery injury.4,27,32 Risk of compression or sacrifice of the C2 nerve roots.43  Bilateral, crossing C2 translaminar screw placement  Wright1 (2004)  Can be used in the setting of aberrant vertebral artery. Decreased risk to vertebral artery compared to earlier screw methods.3 In large case series, high fusion rate (97.6%)3 and lower breach of C2 lamina (1.3%) compared to pedicle screws (7%).45  Increased incidence of reoperation (6.1%) when used in subaxial constructs when compared to pedicle screws (0%).45 Risk of violation of inner laminar cortex with screw placement.34  C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1  Current series (2016)  Decreased risk to vertebral artery and C2 nerve roots compared to earlier screw fixation methods. Can be used in the setting of aberrant vertebral artery. Technical feasibility. Allows for direct visual monitoring of laminar cortical bone to avoid breach.  Not amenable in cases of C1 arch fracture or bifid C1 arch.  Technique  Surgeon, Ref. (year)  Advantage  Shortcoming  Wire or cable placement    Stout braided silk to fasten the posterior arch of C1 to spinous process of C2  Mixter and Osgood5 (1910)  Innovative use of wire for stabilization.  Poor stability in all planes, low likelihood of arthrodesis without bone grafting. Prolonged immobilization.  Iliac bone graft placed above C2 spinous process and abutting posterior C1 arch secured by a steel wire looping around C1 posterior arch and C2 spinous process  Gallie6 (1937)  Technical simplicity. Stability with flexion and extension.  Poor rotational stability compared to Brooks and Jenkins and Magerl technique.33 Increased rate of nonunion compared to screw fixation.40,41 Requires postoperative rigid immobilization.33 Difficult to use in posteriorly displaced C1.11  Bilateral iliac crest bone grafts secured with bilateral sublaminar wires looping under posterior arches of C1 and C2  Brooks and Jenkins10 (1978)  Improved fixation compared to the Gallie technique.42 Technical simplicity.  Increased risk of neural injury with passage of 2 bone grafts. Increased rate of nonunion compared to screw fixation.41 Requires postoperative rigid immobilization.33  Sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft  Sonntag11 (1991)  Avoidance of bilateral bone grafts and use of single loop of wire with decreased risk of injury to neural or vascular structures compared to the Gallie and Brooks and Jenkins technique.11  Requires postoperative rigid immobilization.11  Screw Placement  C1–C2 transarticular screw placement  Magerl19 (1987)  First proposed screw fixation method with improved stability and fusion rates over wire fixation alone.16,33 Technically challenging.  Increased risk of vertebral artery injury.3,4,24,27,32 Risk of compression or sacrifice of the C2 nerve roots.43 Risk of damage to the dura.22,44  C1 lateral mass screw placement in combination with C2 pars or pedicle screws with C2  Goel20,21 (1994)  Anatomic alignment of C1–C2 complex not necessary prior to procedure. High fusion rate reported (100%).21 Decreased risk of injury to vertebral artery compared to the Magerl technique.20  Risk of vertebral artery injury.4,27,32 Risk of compression or sacrifice of the C2 nerve roots.43  Bilateral, crossing C2 translaminar screw placement  Wright1 (2004)  Can be used in the setting of aberrant vertebral artery. Decreased risk to vertebral artery compared to earlier screw methods.3 In large case series, high fusion rate (97.6%)3 and lower breach of C2 lamina (1.3%) compared to pedicle screws (7%).45  Increased incidence of reoperation (6.1%) when used in subaxial constructs when compared to pedicle screws (0%).45 Risk of violation of inner laminar cortex with screw placement.34  C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1  Current series (2016)  Decreased risk to vertebral artery and C2 nerve roots compared to earlier screw fixation methods. Can be used in the setting of aberrant vertebral artery. Technical feasibility. Allows for direct visual monitoring of laminar cortical bone to avoid breach.  Not amenable in cases of C1 arch fracture or bifid C1 arch.  View Large METHODS We analyzed the records of patients undergoing atlantoaxial fusion using C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1 performed by the senior author. All patients were followed postoperatively at our institution. Informed consent was obtained prior to surgical intervention. Any identifiable information has been removed for purposes of this report. Description of Technique The patient is placed on the operating room table in the prone position with the neck in neutral alignment and rigidly fixed in place using a Mayfield head holder. Intraoperative lateral X-ray is used to confirm appropriate sagittal alignment. Exposure is carried out from the occiput to C2. The laminae of C1 and C2 are exposed to the medial aspect of the cervical facet joints; therefore, neither the vertebral artery nor the C2 nerve root needs to be exposed or visualized. The sublaminar space of C1 is developed with a small, curved curette. Following the exposure of C1, a soft cable (DePuy Synthes Spine, Raynam, Massachusetts) is passed under C1 in a caudal to rostral direction. A silk tie can first be passed and then tied to the cable in order to facilitate the cable pass. The C2 translaminar screw (DePuy Synthes Spine, Raynam, Massachusetts) trajectories are prepared using an awl followed by a 3.5 to 4.0 mm tap. Using a hand drill, screws (average length 22-26 mm) are then advanced in the plane of the C2 lamina.1 The contour of the lamina can be observed by the drill operator, which allows direct monitoring of breaching of the laminar cortical bone. Once both of the translaminar C2 screws are in place, short, straight rods are affixed to the C2 screws. Rod length and position is selected in order to match the desired C1–C2 angulation. Small rod connectors are fixed to the C2 screw heads such that the connectors terminate in the axial plane passing through the C1 posterior arch (see Figure 1). Careful inspection is made to assure that the connectors do not extend too far superiorly such that normal head extension would be impeded by the contact between the occiput and the connectors. The cables are then threaded through the holes of the connector rods and tightened using a crimper and fastener. This maneuver reduces the deformity, where C1 is brought into line with C2. A lateral X-ray can be obtained at this point to verify reduction has occurred. FIGURE 1. View largeDownload slide Stepwise schematic of C1–C2 fusion using C2 translaminar screws and C1 sublaminar cables. A, First, crossing C2 translaminar screws are placed; then, B, rods are secured to the C2 screw heads. C, The sublaminar C1 cables are then secured to the superior rod end by passing the cable through the connector holes and fastened using a crimping device. D, Side view of the construct is shown. E, Enlarged view of dual aperture connector used to secure the cable to rod. FIGURE 1. View largeDownload slide Stepwise schematic of C1–C2 fusion using C2 translaminar screws and C1 sublaminar cables. A, First, crossing C2 translaminar screws are placed; then, B, rods are secured to the C2 screw heads. C, The sublaminar C1 cables are then secured to the superior rod end by passing the cable through the connector holes and fastened using a crimping device. D, Side view of the construct is shown. E, Enlarged view of dual aperture connector used to secure the cable to rod. The laminae of C1 and C2 are then decorticated, and either autograft from iliac crest harvest or allograft is placed within the C1–C2 interlaminar space to facilitate arthrodesis. Demineralized bone matrix is also placed over the C1–C2 junction. RESULTS Three patients underwent atlantoaxial fusion using C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1 (see Table 2). All patients were followed postoperatively at our institution. Postoperative imaging was obtained including computed tomography (CT) imaging and flexion and extension X-rays to assess stability of the construct (see Figure 2). FIGURE 2. View largeDownload slide Representative postoperative CT imaging A, flexion B, and extension. C, X-rays demonstrate posterior fusion construct that maintains stable ADI upon dynamic testing. FIGURE 2. View largeDownload slide Representative postoperative CT imaging A, flexion B, and extension. C, X-rays demonstrate posterior fusion construct that maintains stable ADI upon dynamic testing. TABLE 2. Summary of Cases Patient  Etiology of injury  Presenting symptoms  Reason for surgery  Indication for translaminar screws  Outcome  75F  Fall  Limited range of motion and tenderness of cervical spine, cervicalgia  C1–C2 rotatory subluxation with increased ADI (8 mm) and repeat subluxation after closed reduction  Small C1 ring difficult to insert C1 screws  Ongoing fusion, bony bridging between bone graft and C2, bone graft well incorporated into C2 but no definitive incorporation in C1 (6 mo FU)  74F  Arthritic degeneration  Occipital headache, cervicalgia, PICA infarct, dissection of vertebral artery  C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion  Extensive erosion, dissected vertebral artery  Correction of ADI (3 mm), posterior fusion and progressive degeneration (2.5 yr FU)  84M  Fall  Midline neck pain  Odontoid fracture type II with nonunion after 6 wk collar immobilization  Problem with the use of screw in C1  Good fixation at C1–C2, healing of odontoid fracture at the level of bone, and excellent neck rotation, flexion, and extension (3 mo FU)  Patient  Etiology of injury  Presenting symptoms  Reason for surgery  Indication for translaminar screws  Outcome  75F  Fall  Limited range of motion and tenderness of cervical spine, cervicalgia  C1–C2 rotatory subluxation with increased ADI (8 mm) and repeat subluxation after closed reduction  Small C1 ring difficult to insert C1 screws  Ongoing fusion, bony bridging between bone graft and C2, bone graft well incorporated into C2 but no definitive incorporation in C1 (6 mo FU)  74F  Arthritic degeneration  Occipital headache, cervicalgia, PICA infarct, dissection of vertebral artery  C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion  Extensive erosion, dissected vertebral artery  Correction of ADI (3 mm), posterior fusion and progressive degeneration (2.5 yr FU)  84M  Fall  Midline neck pain  Odontoid fracture type II with nonunion after 6 wk collar immobilization  Problem with the use of screw in C1  Good fixation at C1–C2, healing of odontoid fracture at the level of bone, and excellent neck rotation, flexion, and extension (3 mo FU)  ADI: atlanto-dental interval; FU: follow-up; PICA: posterior inferior cerebellar artery. View Large TABLE 2. Summary of Cases Patient  Etiology of injury  Presenting symptoms  Reason for surgery  Indication for translaminar screws  Outcome  75F  Fall  Limited range of motion and tenderness of cervical spine, cervicalgia  C1–C2 rotatory subluxation with increased ADI (8 mm) and repeat subluxation after closed reduction  Small C1 ring difficult to insert C1 screws  Ongoing fusion, bony bridging between bone graft and C2, bone graft well incorporated into C2 but no definitive incorporation in C1 (6 mo FU)  74F  Arthritic degeneration  Occipital headache, cervicalgia, PICA infarct, dissection of vertebral artery  C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion  Extensive erosion, dissected vertebral artery  Correction of ADI (3 mm), posterior fusion and progressive degeneration (2.5 yr FU)  84M  Fall  Midline neck pain  Odontoid fracture type II with nonunion after 6 wk collar immobilization  Problem with the use of screw in C1  Good fixation at C1–C2, healing of odontoid fracture at the level of bone, and excellent neck rotation, flexion, and extension (3 mo FU)  Patient  Etiology of injury  Presenting symptoms  Reason for surgery  Indication for translaminar screws  Outcome  75F  Fall  Limited range of motion and tenderness of cervical spine, cervicalgia  C1–C2 rotatory subluxation with increased ADI (8 mm) and repeat subluxation after closed reduction  Small C1 ring difficult to insert C1 screws  Ongoing fusion, bony bridging between bone graft and C2, bone graft well incorporated into C2 but no definitive incorporation in C1 (6 mo FU)  74F  Arthritic degeneration  Occipital headache, cervicalgia, PICA infarct, dissection of vertebral artery  C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion  Extensive erosion, dissected vertebral artery  Correction of ADI (3 mm), posterior fusion and progressive degeneration (2.5 yr FU)  84M  Fall  Midline neck pain  Odontoid fracture type II with nonunion after 6 wk collar immobilization  Problem with the use of screw in C1  Good fixation at C1–C2, healing of odontoid fracture at the level of bone, and excellent neck rotation, flexion, and extension (3 mo FU)  ADI: atlanto-dental interval; FU: follow-up; PICA: posterior inferior cerebellar artery. View Large Case 1 A 75-yr-old woman presented after falling down stairs with complaints of cervicalgia and decreased range of motion in her neck. She first underwent closed reduction, but repeat subluxation subsequently occurred. She was found to have C1–C2 rotatory subluxation with increased (8 mm) atlantodental interval (ADI). The patient was noted to have a small C1 ring, which would make C1 pedicle or pars screw placement challenging. The patient had no postoperative complications, and her latest CT scan 6 mo postoperatively demonstrated ongoing fusion. Case 2 A 74-yr-old woman presented after developing cervicalgia, vomiting, gait disturbance, and occipital headache. Diagnostic imaging revealed C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion and dissection of the vertebral artery with associated posterior inferior cerebellar artery infarct. Arthritic degeneration of the C1–C2 junction increased the laxity of the joint, which led to vertebral artery trauma and dissection. The described procedure was utilized in this case due to the extensive erosion of the atlantoaxial joint and the underlying vertebral artery injury. The patient had no postoperative complications, and her latest CT scan 2.5 yr postoperatively demonstrated correction of ADI (3 mm) and presence of posterior fusion with no hardware migration. Case 3 An 84-yr-old man presented with midline neck pain from a fall and was found to have type II odontoid fracture. He was initially treated with rigid collar immobilization for 6 wk, but interval imaging showed no evidence of fracture healing. The patient had no postoperative complications, and his flexion and extension X-ray 3 mo postoperatively indicated good fixation at C1–C2, with healing of odontoid fracture at the level of the odontoid bone and no hardware migration. DISCUSSION In 2004, Wright proposed a technique for incorporating C2 into subaxial fusion constructs by using bilateral, crossing C2 translaminar screw placement. As we have also found, the technique requires less lateral exposure and places the vertebral artery and C2 nerve root at almost no risk of injury.1,26 Here, we report the feasibility of using C1 sublaminar cables fixed to C2 translaminar screws. This procedure provides a semirigid, screw-based fusion approach but requires only minimal lateral exposure. Therefore, the major advantages of this technique over previously described approaches are the minimized risk of vertebral artery injury and the complete preservation of C2 nerve root. Past studies evaluating the complications of C1–C2 transarticular screw fixation demonstrate an approximate 4% risk of vertebral artery injury per patient.27 While we only present 3 cases, none of which included a complication, we feel that our technique is simple and merits further examination. This is supported by Dorward and Wright's3 paper that identified no instances of vascular or neurological injuries in 52 patients who underwent C2 translaminar screw placement as part of C2-subaxial fusion. Furthermore, this technique can be used in the setting of an aberrant vertebral artery and has been shown safe for use in the pediatric population.28 It also provides an alternative to C2 pars or pedicle screw placement when anatomy proves unfavorable, as was noted on preoperative imaging for case 2. As illustrated in Figure 2, postoperative flexion and extension X-rays and CT scan demonstrated the posterior fusion construct maintaining a stable ADI upon dynamic testing. The biomechanics of this technique consist of a fixed moment arm cantilever anchored at C2 from which the C1 cable is suspended. This fixed moment arm allows for intraoperative reduction of C1 upon C2, as cable tightening resists anterior translation of C1 on C2 despite no rigid screw fixation in C1. As the crimper tightens the cable, the surgeon can visualize the incremental reduction as C1 is translated posteriorly toward the rod connectors. Additional cross-linking between the connector rods could be considered for additional stability. However, it may prove technically difficult to insert a cross-link in the limited space between C1 and C2, which is occupied by the bone graft. The variable cable tension allows for patient-specific reduction in patients with increased ADI, as described in case 1 and case 2.29-31 Rod length and positioning also allows the surgeon to tailor the C1–C2 angle, a parameter that has been demonstrated to be important in avoiding adjacent-level degeneration in the cervical spine.32 This technique is not amenable, however, in the setting of C1 arch fractures, as the cables would not be reliably secured to the C1 anterior elements and progressive tightening of the C1 would potentially contribute to worsening fracture displacement. Additionally, caution should be used in applying this technique in patients with a bifid C1 arch, as the sublaminar cables may be less reliably fastened to C1 in the setting of the bony defect. The approach allows for a direct view of posterior and anterior laminar cortical bone and recognition of a breach. Because the instrumentation is placed under direct visualization, there is no need for fluoroscopy or for navigation. Gluf et al,4 Madawi et al,33 and Grob et al34 have reported complication rates of 1.4%, 14%, and 15% for screw malposition, respectively, in traditional screw arthrodesis. Because translaminar screws traverse entirely within the posterior elements, the likelihood of an unappreciated intraoperative screw malposition is felt to be less likely than in traditional techniques. Some authors have even proposed the use of “exit” windows placed at the facet-laminar junctions to visualize the final location of the C2 screw tip.35 The technique does require close preoperative inspection of lamina shape and thickness in order assess whether the patient's anatomy will allow for screw placement without lamina perforation.36,37 The use of CT is accurate for determining laminar thickness and should be used in both pediatric and adult populations.38,39 Dorward et al3 report a 2.9% rate of laminar perforation in their study.27 Thick laminae with minimal curvature are more amenable to translaminar screw placement. Cadaveric studies have estimated that approximately 37% and 47% of spines are not able to accommodate 3.5-mm screws and 4-mm laminar screws, respectively, when requiring that 1 mm of bone thickness remains intact around the screw. Furthermore, the average maximal screw length was 32 mm (range 27-37 mm).36 While the C2 laminar fixation technique is relatively new, other authors have reported early clinical results and complications associated with translaminar screw placement.40 In a series of 30 patients, postoperative CT scans found 11 cases (37%) of dorsal laminar breach and 2 cases (7%) of hardware failure.40 The first patient with hardware failure had experienced a fall on ground level 3 mo postoperatively that fractured one of the C2 screws. The second patient was asymptomatic, but routine X-ray 6 mo postoperatively identified a fracture of one of the C3 screws. These early titanium fractures are more indicative of excessive strain and stress placed on the hardware that exceeds screws’ capacity to withstand these forces, and Wang et al40 suggest the use of larger diameter screws to reduce the chance of hardware failure. CONCLUSION Here, we describe a straightforward technique for C1–C2 arthrodesis in the setting of atlantoaxial instability. The technique adopts the translaminar C2 screw placement previously described by Wright et al1 for C1–C2 fusion by combining C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1. This technique dually allows for semirigid fixation and reduction in cases of atlantoaxial instability while also avoiding injury to the vertebral artery and dissection or sacrifice of the C2 nerve root. Our initial experience shows that this is a relatively easy and safe technique for C1–C2 fusion and also adds to the previously described application of C2 translaminar screw placement already described in the literature. We initially adopted this technique in patients in whom the anatomy posed a challenge to traditional C1–C2 fixation. Encouraged by its feasibility, we plan to expand its use. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Wright NM. Posterior C2 fixation using bilateral, crossing C2 laminar screws: case series and technical note. J Spinal Disord Tech.  2004; 17( 2): 158- 162. Google Scholar CrossRef Search ADS PubMed  2. Jacobson ME, Khan SN, An HS. C1-C2 posterior fixation: indications, technique, and results. Orthop Clin North Am.  2012; 43( 1): 11-18, vii. Google Scholar CrossRef Search ADS   3. Dorward IG, Wright NM. Seven years of experience with C2 translaminar screw fixation: clinical series and review of the literature. Neurosurgery.  2011; 68( 6): 1491- 1499; discussion 1499. Google Scholar CrossRef Search ADS PubMed  4. Gluf WM, Schmidt MH, Apfelbaum RI. Atlantoaxial transarticular screw fixation: a review of surgical indications, fusion rate, complications, and lessons learned in 191 adult patients. 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J Bone Joint Surg Am.  1978; 60( 3): 279- 284. Google Scholar CrossRef Search ADS PubMed  11. Dickman CA, Sonntag VK, Papadopoulos SM, Hadley MN. The interspinous method of posterior atlantoaxial arthrodesis. J Neurosurg.  1991; 74( 2): 190- 198. Google Scholar CrossRef Search ADS PubMed  12. Mitchell TC, Sadasivan KK, Ogden AL, Mayeux RH, Mukherjee DP, Albright JA. Biomechanical study of atlantoaxial arthrodesis: transarticular screw fixation versus modified Brooks posterior wiring. J Orthop Trauma.  1999; 13( 7): 483- 489. Google Scholar CrossRef Search ADS PubMed  13. Sim HB, Lee JW, Park JT, Mindea SA, Lim J, Park J. Biomechanical evaluations of various c1-c2 posterior fixation techniques. Spine.  2011; 36( 6): E401- E407. Google Scholar CrossRef Search ADS PubMed  14. Henriques T, Cunningham BW, Olerud C et al.   Biomechanical comparison of five different atlantoaxial posterior fixation techniques. Spine.  2000; 25( 22): 2877- 2883. Google Scholar CrossRef Search ADS PubMed  15. Naderi S, Crawford NR, Song GS, Sonntag VK, Dickman CA. Biomechanical comparison of C1-C2 posterior fixations. Cable, graft, and screw combinations. Spine.  1998; 23( 18): 1946- 1955; discussion 1955-1946. Google Scholar CrossRef Search ADS PubMed  16. Melcher RP, Puttlitz CM, Kleinstueck FS, Lotz JC, Harms J, Bradford DS. Biomechanical testing of posterior atlantoaxial fixation techniques. Spine.  2002; 27( 22): 2435- 2440. Google Scholar CrossRef Search ADS PubMed  17. Richter M, Schmidt R, Claes L, Puhl W, Wilke HJ. Posterior atlantoaxial fixation: biomechanical in vitro comparison of six different techniques. Spine.  2002; 27( 16): 1724- 1732. Google Scholar CrossRef Search ADS PubMed  18. Elgafy H, Potluri T, Goel VK, Foster S, Faizan A, Kulkarni N. Biomechanical analysis comparing three C1-C2 transarticular screw salvaging fixation techniques. Spine.  2010; 35( 4): 378- 385. Google Scholar CrossRef Search ADS PubMed  19. Magerl, F, Seemann, PS. Stable posterior fusion of the atlas and axis by transarticular screw fixation. In: Kehr, P, Weidner, A, ed. Cervical Spine I . New York, NY: Springer; 1987: 322- 327. Google Scholar CrossRef Search ADS   20. Goel A, Laheri V. Plate and screw fixation for atlanto-axial subluxation. Acta Neurochir.  1994; 129( 1-2): 47- 53. Google Scholar CrossRef Search ADS   21. Goel A, Desai KI, Muzumdar DP. Atlantoaxial fixation using plate and screw method: a report of 160 treated patients. Neurosurgery.  2002; 51( 6): 1351- 1356; discussion 1356-1357. Google Scholar CrossRef Search ADS PubMed  22. Bahadur R, Goyal T, Dhatt SS, Tripathy SK. Transarticular screw fixation for atlantoaxial instability - modified Magerl's technique in 38 patients. J Orthop Surg Res.  2010; 5: 1- 8. Google Scholar CrossRef Search ADS PubMed  23. Elliott RE, Tanweer O, Boah A et al.   Outcome comparison of atlantoaxial fusion with transarticular screws and screw-rod constructs: meta-analysis and review of literature. J Spinal Disord Tech.  2014; 27( 1): 11- 28. Google Scholar CrossRef Search ADS PubMed  24. Neo M, Fujibayashi S, Miyata M, Takemoto M, Nakamura T. Vertebral artery injury during cervical spine surgery: a survey of more than 5600 operations. Spine.  2008; 33( 7): 779- 785. Google Scholar CrossRef Search ADS PubMed  25. Yoshida M, Neo M, Fujibayashi S, Nakamura T. Comparison of the anatomical risk for vertebral artery injury associated with the C2-pedicle screw and atlantoaxial transarticular screw. Spine.  2006; 31( 15): E513- E517. Google Scholar CrossRef Search ADS PubMed  26. Wright NM. Translaminar rigid screw fixation of the axis. Technical note. J Neurosurg Spine.  2005; 3( 5): 409- 414. Google Scholar CrossRef Search ADS PubMed  27. Wright NM, Lauryssen C. Vertebral artery injury in C1-2 transarticular screw fixation: results of a survey of the AANS/CNS section on disorders of the spine and peripheral nerves. American Association of Neurological Surgeons/Congress of Neurological Surgeons. J Neurosurg.  1998; 88( 4): 634- 640. Google Scholar CrossRef Search ADS PubMed  28. Chamoun RB, Relyea KM, Johnson KK et al.   Use of axial and subaxial translaminar screw fixation in the management of upper cervical spinal instability in a series of 7 children. Neurosurgery.  2009; 64( 4): 734- 739; discussion 739. Google Scholar CrossRef Search ADS PubMed  29. Gordon L, Matsui J, McDonald E, Gordon JA, Neimkin R. Analysis of a knotless flexor tendon repair using a multifilament stainless steel cable-crimp system. J Hand Surg Am.  2013; 38( 4): 677- 683. Google Scholar CrossRef Search ADS PubMed  30. Schafer MF, Page D, Shen G. Mechanical evaluation of the Dwyer screw-cable attachment. Spine.  1979; 4( 5): 398- 400. Google Scholar CrossRef Search ADS PubMed  31. Huhn SL, Wolf AL, Ecklund J. Posterior spinal osteosynthesis for cervical fracture/dislocation using a flexible multistrand cable system: technical note. Neurosurgery.  1991; 29( 6): 943- 946. Google Scholar CrossRef Search ADS PubMed  32. Yoshida G, Kamiya M, Yoshihara H et al.   Subaxial sagittal alignment and adjacent-segment degeneration after atlantoaxial fixation performed using C-1 lateral mass and C-2 pedicle screws or transarticular screws. J Neurosurg Spine.  2010; 13( 4): 443- 450. Google Scholar CrossRef Search ADS PubMed  33. Madawi AA, Casey AT, Solanki GA, Tuite G, Veres R, Crockard HA. Radiological and anatomical evaluation of the atlantoaxial transarticular screw fixation technique. J Neurosurg.  1997; 86( 6): 961- 968. Google Scholar CrossRef Search ADS PubMed  34. Grob D, Crisco JJ 3rd, Panjabi MM, Wang P, Dvorak J. Biomechanical evaluation of four different posterior atlantoaxial fixation techniques. Spine.  1992; 17( 5): 480- 490. Google Scholar CrossRef Search ADS PubMed  35. Jea A, Sheth RN, Vanni S, Green BA, Levi AD. Modification of Wright's technique for placement of bilateral crossing C2 translaminar screws: technical note. Spine J.  2008; 8( 4): 656- 660. Google Scholar CrossRef Search ADS PubMed  36. Wang MY. C2 crossing laminar screws: cadaveric morphometric analysis. Neurosurgery.  2006; 59( 1 suppl 1): ONS84- ONS88; discussion ONS84-ONS88. Google Scholar PubMed  37. Cassinelli EH, Lee M, Skalak A, Ahn NU, Wright NM. Anatomic considerations for the placement of C2 laminar screws. Spine.  2006; 31( 24): 2767- 2771. Google Scholar CrossRef Search ADS PubMed  38. Dean CL, Lee MJ, Robbin M, Cassinelli EH. Correlation between computed tomography measurements and direct anatomic measurements of the axis for consideration of C2 laminar screw placement. Spine J.  2009; 9( 3): 258- 262. Google Scholar CrossRef Search ADS PubMed  39. Chern JJ, Chamoun RB, Whitehead WE, Curry DJ, Luerssen TG, Jea A. Computed tomography morphometric analysis for axial and subaxial translaminar screw placement in the pediatric cervical spine. J Neurosurg Pediatr.  2009; 3( 2): 121- 128. Google Scholar CrossRef Search ADS PubMed  40. Wang MY. Cervical crossing laminar screws: early clinical results and complications. Neurosurgery.  2007; 61( 5 suppl 2): 311- 315; discussion 315-316. Google Scholar PubMed  41. Coyne TJ, Fehlings MG, Wallace MC, Bernstein M, Tator CH. C1-C2 posterior cervical fusion: long-term evaluation of results and efficacy. Neurosurgery.  1995; 37( 4): 688- 692; discussion 692-693. Google Scholar CrossRef Search ADS PubMed  42. Hanley EN Jr, Harvell JC Jr. Immediate postoperative stability of the atlantoaxial articulation: a biomechanical study comparing simple midline wiring, and the Gallie and Brooks procedures. J Spinal Disord.  1992; 5( 3): 306- 310. Google Scholar CrossRef Search ADS PubMed  43. Huang DG, Hao DJ, Li GL, Guo H, Zhang YC, He BR. C2 nerve dysfunction associated with C1 lateral mass screw fixation. Orthop Surg. . 2014; 6( 4): 269- 273. Google Scholar CrossRef Search ADS PubMed  44. Suchomel P, Stulik J, Klézl Z et al.   [Transarticular fixation of C1-C2: a multicenter retrospective study]. Acta Chir Orthop Traumatol Cech . 2004; 71( 1): 6- 12. Google Scholar PubMed  45. Parker SL, McGirt MJ, Garces-Ambrossi GL et al.   Translaminar versus pedicle screw fixation of C2: comparison of surgical morbidity and accuracy of 313 consecutive screws. Neurosurgery.  2009; 64( 5 suppl 2): 343- 348; discussion 348-349. Google Scholar PubMed  Copyright © 2017 by the Congress of Neurological Surgeons This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Operative Neurosurgery Oxford University Press

Atlantoaxial Fusion Using C1 Sublaminar Cables and C2 Translaminar Screws

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Congress of Neurological Surgeons
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Copyright © 2017 by the Congress of Neurological Surgeons
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2332-4252
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2332-4260
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10.1093/ons/opx164
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Abstract

Abstract BACKGROUND Atlantoaxial instability, which can arise in the setting of trauma, degenerative diseases, and neoplasm, is often managed surgically with C1–C2 arthrodesis. Classical C1–C2 fusion techniques require placement of instrumentation in close proximity to the vertebral artery and C2 nerve root. OBJECTIVE To report a novel C1–C2 fusion technique that utilizes C2 translaminar screws and C1 sublaminar cables to decrease the risk of injury to the vertebral artery and C2 nerve root. METHODS To facilitate fixation to the atlas, while minimizing the risk of injury to the vertebral artery and to the C2 nerve root, we sought to determine the feasibility of using a soft cable around the C1 arch and affixing it to a rod connected to C2 laminar screws. We reviewed our experience in 3 patients. RESULTS We used this technique in patients in whom we anticipated difficult C1 screw placement. Three patients were identified through a review of the senior author's cases. Atlantoaxial instability was associated with trauma in 2 patients and chronic degenerative changes in 1 patient. Common symptoms on presentation included pain and limited range of motion. All patients underwent C1–C2 fusion with C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1. There were no reports of postoperative complications or hardware failure. CONCLUSION We demonstrate a novel, technically straightforward approach for C1–C2 fusion that minimizes risk to the vertebral artery and to the C2 nerve root, while still allowing for semirigid fixation in instances of both traumatic and chronic degenerative atlantoaxial instability. Arthrodesis, Atlantoaxial instability, Fusion, Translaminar ABBREAVIATIONS ABBREAVIATIONS ADI atlantodental interval CT computed tomography Atlantoaxial instability is a condition that arises in a variety of pathologies including trauma, neoplasm, congenital malformations, and degenerative and inflammatory diseases.1-4 Surgical techniques for atlantoaxial fusion have evolved over many decades (see Table 1) since the first technique utilizing stout braided silk to fasten the posterior arch of C1 to the spinous process of C2 was described by Mixter and Osgood in 1910.5 In 1937, Gallie6,7 expanded upon this method by using a threaded steel wire in a similar conformation, and also using the wire to stabilize autologous iliac bone graft placed within the posterior elements of C1 and C2.8,9 Other popular wiring techniques include the Brooks and Jenkins (bilateral iliac crest bone grafts with bilateral sublaminar wires)10 and the Sonntag (sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft).11 Screw fixation methods, which are associated with higher rates of fusion, were later developed.12-18 The techniques include C1–C2 transarticular screw placement (Magerl)19 and C1 lateral mass screw placement in combination with C2 pars or pedicle screws (Goel20,21). However, these techniques increase the risk of vertebral artery injury and can involve either compression or sacrifice of the C2 nerve roots.22-25 An alternative method of fixation to C2 involving translaminar screw placement was described by Wright et al in 2004.1 This method avoids the risk of a vertebral artery injury and has been used as a basis for C1–C2 constructs involving C1 lateral mass screws and C2-subaxial cervical spine fusion constructions. We have since adapted the translaminar C2 screw technique in combination with C1 translaminar cable suspension for C1–C2 fusion in the setting of atlantoaxial instability. This technique offers technical simplicity and decreases the risk of vertebral artery injury while also obviating C2 nerve root sacrifice or compression. Here, we describe our technique and initial success in the treatment of patients with atlantoaxial instability. TABLE 1. Historical Summary of Techniques for C1–C2 Fixation Technique  Surgeon, Ref. (year)  Advantage  Shortcoming  Wire or cable placement    Stout braided silk to fasten the posterior arch of C1 to spinous process of C2  Mixter and Osgood5 (1910)  Innovative use of wire for stabilization.  Poor stability in all planes, low likelihood of arthrodesis without bone grafting. Prolonged immobilization.  Iliac bone graft placed above C2 spinous process and abutting posterior C1 arch secured by a steel wire looping around C1 posterior arch and C2 spinous process  Gallie6 (1937)  Technical simplicity. Stability with flexion and extension.  Poor rotational stability compared to Brooks and Jenkins and Magerl technique.33 Increased rate of nonunion compared to screw fixation.40,41 Requires postoperative rigid immobilization.33 Difficult to use in posteriorly displaced C1.11  Bilateral iliac crest bone grafts secured with bilateral sublaminar wires looping under posterior arches of C1 and C2  Brooks and Jenkins10 (1978)  Improved fixation compared to the Gallie technique.42 Technical simplicity.  Increased risk of neural injury with passage of 2 bone grafts. Increased rate of nonunion compared to screw fixation.41 Requires postoperative rigid immobilization.33  Sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft  Sonntag11 (1991)  Avoidance of bilateral bone grafts and use of single loop of wire with decreased risk of injury to neural or vascular structures compared to the Gallie and Brooks and Jenkins technique.11  Requires postoperative rigid immobilization.11  Screw Placement  C1–C2 transarticular screw placement  Magerl19 (1987)  First proposed screw fixation method with improved stability and fusion rates over wire fixation alone.16,33 Technically challenging.  Increased risk of vertebral artery injury.3,4,24,27,32 Risk of compression or sacrifice of the C2 nerve roots.43 Risk of damage to the dura.22,44  C1 lateral mass screw placement in combination with C2 pars or pedicle screws with C2  Goel20,21 (1994)  Anatomic alignment of C1–C2 complex not necessary prior to procedure. High fusion rate reported (100%).21 Decreased risk of injury to vertebral artery compared to the Magerl technique.20  Risk of vertebral artery injury.4,27,32 Risk of compression or sacrifice of the C2 nerve roots.43  Bilateral, crossing C2 translaminar screw placement  Wright1 (2004)  Can be used in the setting of aberrant vertebral artery. Decreased risk to vertebral artery compared to earlier screw methods.3 In large case series, high fusion rate (97.6%)3 and lower breach of C2 lamina (1.3%) compared to pedicle screws (7%).45  Increased incidence of reoperation (6.1%) when used in subaxial constructs when compared to pedicle screws (0%).45 Risk of violation of inner laminar cortex with screw placement.34  C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1  Current series (2016)  Decreased risk to vertebral artery and C2 nerve roots compared to earlier screw fixation methods. Can be used in the setting of aberrant vertebral artery. Technical feasibility. Allows for direct visual monitoring of laminar cortical bone to avoid breach.  Not amenable in cases of C1 arch fracture or bifid C1 arch.  Technique  Surgeon, Ref. (year)  Advantage  Shortcoming  Wire or cable placement    Stout braided silk to fasten the posterior arch of C1 to spinous process of C2  Mixter and Osgood5 (1910)  Innovative use of wire for stabilization.  Poor stability in all planes, low likelihood of arthrodesis without bone grafting. Prolonged immobilization.  Iliac bone graft placed above C2 spinous process and abutting posterior C1 arch secured by a steel wire looping around C1 posterior arch and C2 spinous process  Gallie6 (1937)  Technical simplicity. Stability with flexion and extension.  Poor rotational stability compared to Brooks and Jenkins and Magerl technique.33 Increased rate of nonunion compared to screw fixation.40,41 Requires postoperative rigid immobilization.33 Difficult to use in posteriorly displaced C1.11  Bilateral iliac crest bone grafts secured with bilateral sublaminar wires looping under posterior arches of C1 and C2  Brooks and Jenkins10 (1978)  Improved fixation compared to the Gallie technique.42 Technical simplicity.  Increased risk of neural injury with passage of 2 bone grafts. Increased rate of nonunion compared to screw fixation.41 Requires postoperative rigid immobilization.33  Sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft  Sonntag11 (1991)  Avoidance of bilateral bone grafts and use of single loop of wire with decreased risk of injury to neural or vascular structures compared to the Gallie and Brooks and Jenkins technique.11  Requires postoperative rigid immobilization.11  Screw Placement  C1–C2 transarticular screw placement  Magerl19 (1987)  First proposed screw fixation method with improved stability and fusion rates over wire fixation alone.16,33 Technically challenging.  Increased risk of vertebral artery injury.3,4,24,27,32 Risk of compression or sacrifice of the C2 nerve roots.43 Risk of damage to the dura.22,44  C1 lateral mass screw placement in combination with C2 pars or pedicle screws with C2  Goel20,21 (1994)  Anatomic alignment of C1–C2 complex not necessary prior to procedure. High fusion rate reported (100%).21 Decreased risk of injury to vertebral artery compared to the Magerl technique.20  Risk of vertebral artery injury.4,27,32 Risk of compression or sacrifice of the C2 nerve roots.43  Bilateral, crossing C2 translaminar screw placement  Wright1 (2004)  Can be used in the setting of aberrant vertebral artery. Decreased risk to vertebral artery compared to earlier screw methods.3 In large case series, high fusion rate (97.6%)3 and lower breach of C2 lamina (1.3%) compared to pedicle screws (7%).45  Increased incidence of reoperation (6.1%) when used in subaxial constructs when compared to pedicle screws (0%).45 Risk of violation of inner laminar cortex with screw placement.34  C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1  Current series (2016)  Decreased risk to vertebral artery and C2 nerve roots compared to earlier screw fixation methods. Can be used in the setting of aberrant vertebral artery. Technical feasibility. Allows for direct visual monitoring of laminar cortical bone to avoid breach.  Not amenable in cases of C1 arch fracture or bifid C1 arch.  View Large TABLE 1. Historical Summary of Techniques for C1–C2 Fixation Technique  Surgeon, Ref. (year)  Advantage  Shortcoming  Wire or cable placement    Stout braided silk to fasten the posterior arch of C1 to spinous process of C2  Mixter and Osgood5 (1910)  Innovative use of wire for stabilization.  Poor stability in all planes, low likelihood of arthrodesis without bone grafting. Prolonged immobilization.  Iliac bone graft placed above C2 spinous process and abutting posterior C1 arch secured by a steel wire looping around C1 posterior arch and C2 spinous process  Gallie6 (1937)  Technical simplicity. Stability with flexion and extension.  Poor rotational stability compared to Brooks and Jenkins and Magerl technique.33 Increased rate of nonunion compared to screw fixation.40,41 Requires postoperative rigid immobilization.33 Difficult to use in posteriorly displaced C1.11  Bilateral iliac crest bone grafts secured with bilateral sublaminar wires looping under posterior arches of C1 and C2  Brooks and Jenkins10 (1978)  Improved fixation compared to the Gallie technique.42 Technical simplicity.  Increased risk of neural injury with passage of 2 bone grafts. Increased rate of nonunion compared to screw fixation.41 Requires postoperative rigid immobilization.33  Sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft  Sonntag11 (1991)  Avoidance of bilateral bone grafts and use of single loop of wire with decreased risk of injury to neural or vascular structures compared to the Gallie and Brooks and Jenkins technique.11  Requires postoperative rigid immobilization.11  Screw Placement  C1–C2 transarticular screw placement  Magerl19 (1987)  First proposed screw fixation method with improved stability and fusion rates over wire fixation alone.16,33 Technically challenging.  Increased risk of vertebral artery injury.3,4,24,27,32 Risk of compression or sacrifice of the C2 nerve roots.43 Risk of damage to the dura.22,44  C1 lateral mass screw placement in combination with C2 pars or pedicle screws with C2  Goel20,21 (1994)  Anatomic alignment of C1–C2 complex not necessary prior to procedure. High fusion rate reported (100%).21 Decreased risk of injury to vertebral artery compared to the Magerl technique.20  Risk of vertebral artery injury.4,27,32 Risk of compression or sacrifice of the C2 nerve roots.43  Bilateral, crossing C2 translaminar screw placement  Wright1 (2004)  Can be used in the setting of aberrant vertebral artery. Decreased risk to vertebral artery compared to earlier screw methods.3 In large case series, high fusion rate (97.6%)3 and lower breach of C2 lamina (1.3%) compared to pedicle screws (7%).45  Increased incidence of reoperation (6.1%) when used in subaxial constructs when compared to pedicle screws (0%).45 Risk of violation of inner laminar cortex with screw placement.34  C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1  Current series (2016)  Decreased risk to vertebral artery and C2 nerve roots compared to earlier screw fixation methods. Can be used in the setting of aberrant vertebral artery. Technical feasibility. Allows for direct visual monitoring of laminar cortical bone to avoid breach.  Not amenable in cases of C1 arch fracture or bifid C1 arch.  Technique  Surgeon, Ref. (year)  Advantage  Shortcoming  Wire or cable placement    Stout braided silk to fasten the posterior arch of C1 to spinous process of C2  Mixter and Osgood5 (1910)  Innovative use of wire for stabilization.  Poor stability in all planes, low likelihood of arthrodesis without bone grafting. Prolonged immobilization.  Iliac bone graft placed above C2 spinous process and abutting posterior C1 arch secured by a steel wire looping around C1 posterior arch and C2 spinous process  Gallie6 (1937)  Technical simplicity. Stability with flexion and extension.  Poor rotational stability compared to Brooks and Jenkins and Magerl technique.33 Increased rate of nonunion compared to screw fixation.40,41 Requires postoperative rigid immobilization.33 Difficult to use in posteriorly displaced C1.11  Bilateral iliac crest bone grafts secured with bilateral sublaminar wires looping under posterior arches of C1 and C2  Brooks and Jenkins10 (1978)  Improved fixation compared to the Gallie technique.42 Technical simplicity.  Increased risk of neural injury with passage of 2 bone grafts. Increased rate of nonunion compared to screw fixation.41 Requires postoperative rigid immobilization.33  Sublaminar C1 wire secured to C2 by crimping over the notch in C2 process along with C1–C2 bone graft  Sonntag11 (1991)  Avoidance of bilateral bone grafts and use of single loop of wire with decreased risk of injury to neural or vascular structures compared to the Gallie and Brooks and Jenkins technique.11  Requires postoperative rigid immobilization.11  Screw Placement  C1–C2 transarticular screw placement  Magerl19 (1987)  First proposed screw fixation method with improved stability and fusion rates over wire fixation alone.16,33 Technically challenging.  Increased risk of vertebral artery injury.3,4,24,27,32 Risk of compression or sacrifice of the C2 nerve roots.43 Risk of damage to the dura.22,44  C1 lateral mass screw placement in combination with C2 pars or pedicle screws with C2  Goel20,21 (1994)  Anatomic alignment of C1–C2 complex not necessary prior to procedure. High fusion rate reported (100%).21 Decreased risk of injury to vertebral artery compared to the Magerl technique.20  Risk of vertebral artery injury.4,27,32 Risk of compression or sacrifice of the C2 nerve roots.43  Bilateral, crossing C2 translaminar screw placement  Wright1 (2004)  Can be used in the setting of aberrant vertebral artery. Decreased risk to vertebral artery compared to earlier screw methods.3 In large case series, high fusion rate (97.6%)3 and lower breach of C2 lamina (1.3%) compared to pedicle screws (7%).45  Increased incidence of reoperation (6.1%) when used in subaxial constructs when compared to pedicle screws (0%).45 Risk of violation of inner laminar cortex with screw placement.34  C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1  Current series (2016)  Decreased risk to vertebral artery and C2 nerve roots compared to earlier screw fixation methods. Can be used in the setting of aberrant vertebral artery. Technical feasibility. Allows for direct visual monitoring of laminar cortical bone to avoid breach.  Not amenable in cases of C1 arch fracture or bifid C1 arch.  View Large METHODS We analyzed the records of patients undergoing atlantoaxial fusion using C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1 performed by the senior author. All patients were followed postoperatively at our institution. Informed consent was obtained prior to surgical intervention. Any identifiable information has been removed for purposes of this report. Description of Technique The patient is placed on the operating room table in the prone position with the neck in neutral alignment and rigidly fixed in place using a Mayfield head holder. Intraoperative lateral X-ray is used to confirm appropriate sagittal alignment. Exposure is carried out from the occiput to C2. The laminae of C1 and C2 are exposed to the medial aspect of the cervical facet joints; therefore, neither the vertebral artery nor the C2 nerve root needs to be exposed or visualized. The sublaminar space of C1 is developed with a small, curved curette. Following the exposure of C1, a soft cable (DePuy Synthes Spine, Raynam, Massachusetts) is passed under C1 in a caudal to rostral direction. A silk tie can first be passed and then tied to the cable in order to facilitate the cable pass. The C2 translaminar screw (DePuy Synthes Spine, Raynam, Massachusetts) trajectories are prepared using an awl followed by a 3.5 to 4.0 mm tap. Using a hand drill, screws (average length 22-26 mm) are then advanced in the plane of the C2 lamina.1 The contour of the lamina can be observed by the drill operator, which allows direct monitoring of breaching of the laminar cortical bone. Once both of the translaminar C2 screws are in place, short, straight rods are affixed to the C2 screws. Rod length and position is selected in order to match the desired C1–C2 angulation. Small rod connectors are fixed to the C2 screw heads such that the connectors terminate in the axial plane passing through the C1 posterior arch (see Figure 1). Careful inspection is made to assure that the connectors do not extend too far superiorly such that normal head extension would be impeded by the contact between the occiput and the connectors. The cables are then threaded through the holes of the connector rods and tightened using a crimper and fastener. This maneuver reduces the deformity, where C1 is brought into line with C2. A lateral X-ray can be obtained at this point to verify reduction has occurred. FIGURE 1. View largeDownload slide Stepwise schematic of C1–C2 fusion using C2 translaminar screws and C1 sublaminar cables. A, First, crossing C2 translaminar screws are placed; then, B, rods are secured to the C2 screw heads. C, The sublaminar C1 cables are then secured to the superior rod end by passing the cable through the connector holes and fastened using a crimping device. D, Side view of the construct is shown. E, Enlarged view of dual aperture connector used to secure the cable to rod. FIGURE 1. View largeDownload slide Stepwise schematic of C1–C2 fusion using C2 translaminar screws and C1 sublaminar cables. A, First, crossing C2 translaminar screws are placed; then, B, rods are secured to the C2 screw heads. C, The sublaminar C1 cables are then secured to the superior rod end by passing the cable through the connector holes and fastened using a crimping device. D, Side view of the construct is shown. E, Enlarged view of dual aperture connector used to secure the cable to rod. The laminae of C1 and C2 are then decorticated, and either autograft from iliac crest harvest or allograft is placed within the C1–C2 interlaminar space to facilitate arthrodesis. Demineralized bone matrix is also placed over the C1–C2 junction. RESULTS Three patients underwent atlantoaxial fusion using C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1 (see Table 2). All patients were followed postoperatively at our institution. Postoperative imaging was obtained including computed tomography (CT) imaging and flexion and extension X-rays to assess stability of the construct (see Figure 2). FIGURE 2. View largeDownload slide Representative postoperative CT imaging A, flexion B, and extension. C, X-rays demonstrate posterior fusion construct that maintains stable ADI upon dynamic testing. FIGURE 2. View largeDownload slide Representative postoperative CT imaging A, flexion B, and extension. C, X-rays demonstrate posterior fusion construct that maintains stable ADI upon dynamic testing. TABLE 2. Summary of Cases Patient  Etiology of injury  Presenting symptoms  Reason for surgery  Indication for translaminar screws  Outcome  75F  Fall  Limited range of motion and tenderness of cervical spine, cervicalgia  C1–C2 rotatory subluxation with increased ADI (8 mm) and repeat subluxation after closed reduction  Small C1 ring difficult to insert C1 screws  Ongoing fusion, bony bridging between bone graft and C2, bone graft well incorporated into C2 but no definitive incorporation in C1 (6 mo FU)  74F  Arthritic degeneration  Occipital headache, cervicalgia, PICA infarct, dissection of vertebral artery  C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion  Extensive erosion, dissected vertebral artery  Correction of ADI (3 mm), posterior fusion and progressive degeneration (2.5 yr FU)  84M  Fall  Midline neck pain  Odontoid fracture type II with nonunion after 6 wk collar immobilization  Problem with the use of screw in C1  Good fixation at C1–C2, healing of odontoid fracture at the level of bone, and excellent neck rotation, flexion, and extension (3 mo FU)  Patient  Etiology of injury  Presenting symptoms  Reason for surgery  Indication for translaminar screws  Outcome  75F  Fall  Limited range of motion and tenderness of cervical spine, cervicalgia  C1–C2 rotatory subluxation with increased ADI (8 mm) and repeat subluxation after closed reduction  Small C1 ring difficult to insert C1 screws  Ongoing fusion, bony bridging between bone graft and C2, bone graft well incorporated into C2 but no definitive incorporation in C1 (6 mo FU)  74F  Arthritic degeneration  Occipital headache, cervicalgia, PICA infarct, dissection of vertebral artery  C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion  Extensive erosion, dissected vertebral artery  Correction of ADI (3 mm), posterior fusion and progressive degeneration (2.5 yr FU)  84M  Fall  Midline neck pain  Odontoid fracture type II with nonunion after 6 wk collar immobilization  Problem with the use of screw in C1  Good fixation at C1–C2, healing of odontoid fracture at the level of bone, and excellent neck rotation, flexion, and extension (3 mo FU)  ADI: atlanto-dental interval; FU: follow-up; PICA: posterior inferior cerebellar artery. View Large TABLE 2. Summary of Cases Patient  Etiology of injury  Presenting symptoms  Reason for surgery  Indication for translaminar screws  Outcome  75F  Fall  Limited range of motion and tenderness of cervical spine, cervicalgia  C1–C2 rotatory subluxation with increased ADI (8 mm) and repeat subluxation after closed reduction  Small C1 ring difficult to insert C1 screws  Ongoing fusion, bony bridging between bone graft and C2, bone graft well incorporated into C2 but no definitive incorporation in C1 (6 mo FU)  74F  Arthritic degeneration  Occipital headache, cervicalgia, PICA infarct, dissection of vertebral artery  C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion  Extensive erosion, dissected vertebral artery  Correction of ADI (3 mm), posterior fusion and progressive degeneration (2.5 yr FU)  84M  Fall  Midline neck pain  Odontoid fracture type II with nonunion after 6 wk collar immobilization  Problem with the use of screw in C1  Good fixation at C1–C2, healing of odontoid fracture at the level of bone, and excellent neck rotation, flexion, and extension (3 mo FU)  Patient  Etiology of injury  Presenting symptoms  Reason for surgery  Indication for translaminar screws  Outcome  75F  Fall  Limited range of motion and tenderness of cervical spine, cervicalgia  C1–C2 rotatory subluxation with increased ADI (8 mm) and repeat subluxation after closed reduction  Small C1 ring difficult to insert C1 screws  Ongoing fusion, bony bridging between bone graft and C2, bone graft well incorporated into C2 but no definitive incorporation in C1 (6 mo FU)  74F  Arthritic degeneration  Occipital headache, cervicalgia, PICA infarct, dissection of vertebral artery  C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion  Extensive erosion, dissected vertebral artery  Correction of ADI (3 mm), posterior fusion and progressive degeneration (2.5 yr FU)  84M  Fall  Midline neck pain  Odontoid fracture type II with nonunion after 6 wk collar immobilization  Problem with the use of screw in C1  Good fixation at C1–C2, healing of odontoid fracture at the level of bone, and excellent neck rotation, flexion, and extension (3 mo FU)  ADI: atlanto-dental interval; FU: follow-up; PICA: posterior inferior cerebellar artery. View Large Case 1 A 75-yr-old woman presented after falling down stairs with complaints of cervicalgia and decreased range of motion in her neck. She first underwent closed reduction, but repeat subluxation subsequently occurred. She was found to have C1–C2 rotatory subluxation with increased (8 mm) atlantodental interval (ADI). The patient was noted to have a small C1 ring, which would make C1 pedicle or pars screw placement challenging. The patient had no postoperative complications, and her latest CT scan 6 mo postoperatively demonstrated ongoing fusion. Case 2 A 74-yr-old woman presented after developing cervicalgia, vomiting, gait disturbance, and occipital headache. Diagnostic imaging revealed C1–C2 lateral subluxation with increased ADI (5 mm) with left-sided C1-ring lesion and dissection of the vertebral artery with associated posterior inferior cerebellar artery infarct. Arthritic degeneration of the C1–C2 junction increased the laxity of the joint, which led to vertebral artery trauma and dissection. The described procedure was utilized in this case due to the extensive erosion of the atlantoaxial joint and the underlying vertebral artery injury. The patient had no postoperative complications, and her latest CT scan 2.5 yr postoperatively demonstrated correction of ADI (3 mm) and presence of posterior fusion with no hardware migration. Case 3 An 84-yr-old man presented with midline neck pain from a fall and was found to have type II odontoid fracture. He was initially treated with rigid collar immobilization for 6 wk, but interval imaging showed no evidence of fracture healing. The patient had no postoperative complications, and his flexion and extension X-ray 3 mo postoperatively indicated good fixation at C1–C2, with healing of odontoid fracture at the level of the odontoid bone and no hardware migration. DISCUSSION In 2004, Wright proposed a technique for incorporating C2 into subaxial fusion constructs by using bilateral, crossing C2 translaminar screw placement. As we have also found, the technique requires less lateral exposure and places the vertebral artery and C2 nerve root at almost no risk of injury.1,26 Here, we report the feasibility of using C1 sublaminar cables fixed to C2 translaminar screws. This procedure provides a semirigid, screw-based fusion approach but requires only minimal lateral exposure. Therefore, the major advantages of this technique over previously described approaches are the minimized risk of vertebral artery injury and the complete preservation of C2 nerve root. Past studies evaluating the complications of C1–C2 transarticular screw fixation demonstrate an approximate 4% risk of vertebral artery injury per patient.27 While we only present 3 cases, none of which included a complication, we feel that our technique is simple and merits further examination. This is supported by Dorward and Wright's3 paper that identified no instances of vascular or neurological injuries in 52 patients who underwent C2 translaminar screw placement as part of C2-subaxial fusion. Furthermore, this technique can be used in the setting of an aberrant vertebral artery and has been shown safe for use in the pediatric population.28 It also provides an alternative to C2 pars or pedicle screw placement when anatomy proves unfavorable, as was noted on preoperative imaging for case 2. As illustrated in Figure 2, postoperative flexion and extension X-rays and CT scan demonstrated the posterior fusion construct maintaining a stable ADI upon dynamic testing. The biomechanics of this technique consist of a fixed moment arm cantilever anchored at C2 from which the C1 cable is suspended. This fixed moment arm allows for intraoperative reduction of C1 upon C2, as cable tightening resists anterior translation of C1 on C2 despite no rigid screw fixation in C1. As the crimper tightens the cable, the surgeon can visualize the incremental reduction as C1 is translated posteriorly toward the rod connectors. Additional cross-linking between the connector rods could be considered for additional stability. However, it may prove technically difficult to insert a cross-link in the limited space between C1 and C2, which is occupied by the bone graft. The variable cable tension allows for patient-specific reduction in patients with increased ADI, as described in case 1 and case 2.29-31 Rod length and positioning also allows the surgeon to tailor the C1–C2 angle, a parameter that has been demonstrated to be important in avoiding adjacent-level degeneration in the cervical spine.32 This technique is not amenable, however, in the setting of C1 arch fractures, as the cables would not be reliably secured to the C1 anterior elements and progressive tightening of the C1 would potentially contribute to worsening fracture displacement. Additionally, caution should be used in applying this technique in patients with a bifid C1 arch, as the sublaminar cables may be less reliably fastened to C1 in the setting of the bony defect. The approach allows for a direct view of posterior and anterior laminar cortical bone and recognition of a breach. Because the instrumentation is placed under direct visualization, there is no need for fluoroscopy or for navigation. Gluf et al,4 Madawi et al,33 and Grob et al34 have reported complication rates of 1.4%, 14%, and 15% for screw malposition, respectively, in traditional screw arthrodesis. Because translaminar screws traverse entirely within the posterior elements, the likelihood of an unappreciated intraoperative screw malposition is felt to be less likely than in traditional techniques. Some authors have even proposed the use of “exit” windows placed at the facet-laminar junctions to visualize the final location of the C2 screw tip.35 The technique does require close preoperative inspection of lamina shape and thickness in order assess whether the patient's anatomy will allow for screw placement without lamina perforation.36,37 The use of CT is accurate for determining laminar thickness and should be used in both pediatric and adult populations.38,39 Dorward et al3 report a 2.9% rate of laminar perforation in their study.27 Thick laminae with minimal curvature are more amenable to translaminar screw placement. Cadaveric studies have estimated that approximately 37% and 47% of spines are not able to accommodate 3.5-mm screws and 4-mm laminar screws, respectively, when requiring that 1 mm of bone thickness remains intact around the screw. Furthermore, the average maximal screw length was 32 mm (range 27-37 mm).36 While the C2 laminar fixation technique is relatively new, other authors have reported early clinical results and complications associated with translaminar screw placement.40 In a series of 30 patients, postoperative CT scans found 11 cases (37%) of dorsal laminar breach and 2 cases (7%) of hardware failure.40 The first patient with hardware failure had experienced a fall on ground level 3 mo postoperatively that fractured one of the C2 screws. The second patient was asymptomatic, but routine X-ray 6 mo postoperatively identified a fracture of one of the C3 screws. These early titanium fractures are more indicative of excessive strain and stress placed on the hardware that exceeds screws’ capacity to withstand these forces, and Wang et al40 suggest the use of larger diameter screws to reduce the chance of hardware failure. CONCLUSION Here, we describe a straightforward technique for C1–C2 arthrodesis in the setting of atlantoaxial instability. The technique adopts the translaminar C2 screw placement previously described by Wright et al1 for C1–C2 fusion by combining C2 translaminar screws with sublaminar cable harnessing of the posterior arch of C1. This technique dually allows for semirigid fixation and reduction in cases of atlantoaxial instability while also avoiding injury to the vertebral artery and dissection or sacrifice of the C2 nerve root. Our initial experience shows that this is a relatively easy and safe technique for C1–C2 fusion and also adds to the previously described application of C2 translaminar screw placement already described in the literature. We initially adopted this technique in patients in whom the anatomy posed a challenge to traditional C1–C2 fixation. Encouraged by its feasibility, we plan to expand its use. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Wright NM. Posterior C2 fixation using bilateral, crossing C2 laminar screws: case series and technical note. J Spinal Disord Tech.  2004; 17( 2): 158- 162. Google Scholar CrossRef Search ADS PubMed  2. Jacobson ME, Khan SN, An HS. C1-C2 posterior fixation: indications, technique, and results. Orthop Clin North Am.  2012; 43( 1): 11-18, vii. Google Scholar CrossRef Search ADS   3. Dorward IG, Wright NM. Seven years of experience with C2 translaminar screw fixation: clinical series and review of the literature. Neurosurgery.  2011; 68( 6): 1491- 1499; discussion 1499. Google Scholar CrossRef Search ADS PubMed  4. Gluf WM, Schmidt MH, Apfelbaum RI. Atlantoaxial transarticular screw fixation: a review of surgical indications, fusion rate, complications, and lessons learned in 191 adult patients. 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Operative NeurosurgeryOxford University Press

Published: Aug 10, 2017

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